1. Field of the Invention
The present invention relates to an alignment stage device capable of aligning the reticle or mask, which has been set on the exposure means in the course of manufacturing semiconductor elements, for example, relative to the projection lenses and the like.
2. Description of the Related Art
The aligning of the reticles or masks which are used to produce the semiconductor elements is usually attained by the alignment stage device which provides motions in plural degree of freedom by plural stages to precisely align the reticles or masks. More specifically, the alignment stage device has X and y stages which can move with the precision of micron order along X and y axes perpendicular to each other on a horizontal plane, and a .theta. stage which can rotate round an axis perpendicular to the horizontal plane. When movements of these stages are combined with one another, the reticle or mask set on this alignment stage device can be aligned relative to the projection lenses and the like.
In the case of the conventional alignment stage device, x, y and .theta. stages are mounted one upon the other and each of them is guided in one direction by a pair of guide members. The height of the whole alignment stage device, therefore, equals to the sum of thicknesses of x, y and .theta. stages and heights of stages bases for supporting x, y and .theta. stages. In addition, the alignment stage device needs a large number of parts to guide these stages.
Further, ultraviolet- and X-rays which are exposed have become shorter and shorter in wavelength as the semiconductor elements and patterns which are exposed and transferred are made finer in size. In order to enhance the precision of controlling the reticles or masks and holding the interval between the reticle and the projection lens, therefore, there has been proposed an alignment stage device provided with further Z stage, which can move up and down, as well as x, y and .theta. stages. When Z stage is added like this, the alignment stage device becomes higher and the device itself becomes larger in size, accordingly. In addition, the number of parts used is increased to guide Z stage.
Although Z stage is added to enhance the control precision, the control precision is reversely reduced because the alignment stage device becomes larger in size. Therefore, the addition of Z stage is not so effective as to enhance the control precision.